The present invention relates to a silver halide photographic material, and particularly to a silver halide photographic material using dopant technology, which has high sensitivity, high gradation and no reciprocity failure.
As one of techniques for modifying silver halide grains to improve the entire performance of silver halide photographic materials so as to be expected, there is a technique of incorporating silver ions and materials other than halide ions (dopants) into the silver halide grains (a doping technique). In particular, many investigations have been conducted for the doping technique of transition metal ions. When the transition metal ions are introduced into the silver halide grains as dopants, it has generally been observed that the transition metal ions effectively change photographic properties even though they are added in an extremely slight amount.
In order to improve the photographic properties of silver halide emulsions more effectively, a technique has also been known in which the silver halide grains are doped with not only the transition metal ions but also transition metal complexes. Effects obtained by the doping technique are (1) increase of sensitivity, (2) improvement in reciprocity failure and (3) increase of contrast. For the purpose of obtaining a highly sensitized emulsion, a group VIII metal complex having a cyanide ion as a ligand is used as a dopant, as disclosed in Japanese Patent Laid-Open No. 20854/1990 and Japanese Patent Publication No. 113743/1995. A hexacyano complex having iron or aluminum as a central metal is an effective sensitizing dopant among others. In order to obtain a high gradation emulsion, there is used a technique using hexachlororuthenium, hexachlororhodium or hexachlororhenium as disclosed in Japanese Patent Laid-Open Nos. 184740/1988, 285941/1989, 20852/1990 and 20855/1990, or a technique using nitrosyl or thionitrosyl as a ligand of a transition metal complex as disclosed in European Patents 033642, 0606895 and 0610670.
On the other hand, iridium complexes are used in order to improve reciprocity failure, particularly high intensity reciprocity failure. Examples of silver halide grains doped with the iridium complexes are disclosed in Japanese Patent Laid-Open Nos. 285941/1989, 118583/1991, 213449/1992, 278940/1992, 66511/1993, 313277/1993, 82947/1994, 235995/1994, 72569/1995, 72576/1995, 202440/1999 and 295841/1999, and a fluoride ion, a chloride ion, a bromide ion, H2O, cyano, nitrosyl and thionitrosyl are used as ligands of the iridium complexes. Further, U.S. Pat. No. 5,360,712 discloses dopant technology using organic compounds as ligands, and discloses an iridium complex (IrCl5(thia)) having thiazole as a ligand, as a dopant for improving high intensity reciprocity failure.
The use of the iridium complexes as dopants like these examples effectively improves high intensity reciprocity failure. However, tries to completely improve the high intensity reciprocity failure in the conventional examples accompany desensitization and decrease of contrast on the low intensity side in all cases, so that it has been difficult to improve the reciprocity failure which occurs at a high illumination, while keeping the photographic characteristics on the low intensity side unchanged.
An object of the present invention is to provide a silver halide photographic material by dopant technology, in which no reciprocity failure occurs over a wide range of exposure illuminations without desensitization and decrease of contrast on the low intensity side. As in the present invention, there are provided:
(1) A light-sensitive silver halide grain containing at least one metal complex having in a ligand a site which can form any bond of a covalent bond, a dative bond and an ionic bond, or a bond in a mixed form of these bonds with a silver ion, wherein when an a-axis, a b-axis and a c-axis of a silver halide crystal lattice are each established taking as an origin a central metal of the metal complex incorporated into the silver halide grain, the site in the ligand can interact with the silver ion on a lattice point which does not exist on any of the a-axis, the b-axis and the c-axis;
(2) The light-sensitive silver halide grain described in (1), wherein the ligand is a ligand which has a volume of 220% to 300% based on the volume of a chloride ion Clxe2x88x92, and in which the distance from an atom in the ligand coordinated to the central metal of the metal complex to an atom in the ligand farthest away is 5.1 angstroms or less;
(3) The light-sensitive silver halide grain described in (2), wherein the ligand is a ligand which has a volume of 220% to 265% based on the volume of a chloride ion Clxe2x88x92, and in which the distance from an atom in the ligand coordinated to the central metal of the metal complex to an atom in the ligand farthest away is 4.7 angstroms or less;
(4) The light-sensitive silver halide grain described in (1), wherein the interactable site in the ligand is from 2.5 angstroms to 4.0 angstroms apart from the silver ion on the lattice point which does not exist on any of the a-axis, the b-axis and the c-axis;
(5) The light-sensitive silver halide grain described in (1), wherein the metal complex has at least one asymmetric ligand, and a substituent group in the ligand occupies a position of a silver ion adjacent to the asymmetric ligand;
(6) The light-sensitive silver halide grain described in (1), wherein the ionic conductivity of the silver halide grain at the time when the metal complex is incorporated into the silver halide grain in an amount of 1xc3x9710xe2x88x924 mol per mol of silver is 50 times or less that of the silver halide grain into which no metal ion or no metal complex is introduced;
(7) The light-sensitive silver halide grain described in (6), wherein the ionic conductivity of the silver halide grain at the time when the metal complex is incorporated into the silver halide grain in an amount of 1xc3x9710xe2x88x924 mol per mol of silver is 30 times or less that of the silver halide grain into which no metal ion or no metal complex is introduced;
(8) The light-sensitive silver halide grain described in (1), wherein the metal complex incorporated into the silver halide grain has a charge more positive than xe2x88x923;
(9) The light-sensitive silver halide grain described in (1), wherein the silver halide grain has an illumination conversion time of 5 seconds or less;
(10) The light-sensitive silver halide grain described in (1), wherein the metal complex is a transition metal complex;
(11) The light-sensitive silver halide grain described in (1), wherein the ligand is an organic compound having 3 or less carbon atoms or an inorganic compound;
(12) The light-sensitive silver halide grain described in (1), wherein the metal complex is an iridium complex;
(13) The light-sensitive silver halide grain described in (1), wherein the metal complex contains at least one ligand selected from the group consisting of a thiadiazole compound, a thiatriazole compound, an oxadiazole compound and a triazole compound;
(14) The light-sensitive silver halide grain described in (1), wherein the ligand of the metal complex contains phosphorus;
(15) The light-sensitive silver halide grain described in (1), wherein the ligand of the metal complex has an Nxe2x80x94Cxe2x80x94S bond;
(16) The light-sensitive silver halide grain described in (1), wherein the silver halide grain is mainly composed of silver chloride;
(17) The light-sensitive silver halide grain described in (1), wherein the silver halide grain has a silver bromide-containing layer, and the metal complex is contained in the silver bromide-containing layer;
(18) The light-sensitive silver halide grain described in (17), wherein the silver bromide-containing layer has a silver bromide content of 5 mol % to 50 mol %;
(19) The light-sensitive silver halide grain described in (16), wherein the silver halide grain has a silver chloride content of 89 mol % to 99.7 mol %, a silver bromide content of 0.25 mol % to 10 mol %, and a silver iodide content of 0.05 mol % to 1 mol %; and
(20) A silver halide emulsion containing the light-sensitive silver halide grain described in (1).